Wine Maturation

Maturation

Most wines undergo some form of aging before release in oak barrels, tanks or in bottle. There are modern techniques, such as micro-oxygenation, that aspire to speed up and re-create the effects of aging, but there is nothing that can replace the effects of time.

Most wines undergo some form of aging before release. Different types of maturation serve different purposes. Barrel maturation is commonly used for aging both reds and whites. The wines are aged in small oak casks that hold approximately 225 liters, known as barriques, a standard capacity in Bordeaux. The 228-liter Burgundy pièce is a slightly different shape, but serves essentially the same purpose, thought the staves are thicker and are often bound with a chestnut hoop. Champagne barrels hold 205 liters.

Oak aging can have three effects on the wine: flavoring that comes from compounds in the wood; improvement in clarity that comes from gradual settling of the wine; and a fixing of the phenolic compounds (polymerization of polyphenols and tannins) due to the slight and gradual exchange of oxygen between the air outside the barrel and the wine. All these effects become more pronounced the longer the wine remains in cask. The net effect and most important consequence of barrel aging during the process of elevage (literally 'raising') is that it accelerates the maturation of the developing wine.

Some wines are aged in larger barrels such as the 900-liter tonneaux, the 600-liter demi-muid (used in Châteauneuf du Pâpe and Languedoc Roussillon), and various types of foudres, puncheons, botti (in Italy), pipes (for Port), and butts (for Sherry). In larger barrels, the ratio of surface to volume is much smaller, and the wine is correspondingly less marked by wood flavor.

Tanks are also used for aging wines. Tanks do not mark the wine in any way, but can be used as vessels for lees aging. In general, they are reductive (stainless steel is not porous) and oxygen can be excluded completely by blanketing the wine with inert gas.

Some winemakers use micro-oxygenation to introduce a certain amount of oxygen without racking. This system injects minute amounts of oxygen into red wine that is aging in tank and encourages the stabilization of phenolic compounds without necessitating racking by hand, therefore serving as a labor-saving device. This is a relatively new method that some winemakers feel can improve the overall quality of fine wines and value wines alike.

In higher doses, micro-oxygenation can make a wine very soft and velvety in texture. It is known for imparting a characteristic chocolaty character to the tannins. This effect can be overdone, however, making the wine unbalanced.

Some winemakers also bottle-age their wines and in some regions, bottle aging is required by law. This type of aging doesn’t polymerize the polyphenols, as in barrel aging, but it does add complexity to the wines by forming esters. Esters, compounds formed by the combination of acids and alcohols, are volatile and contribute to the development of the bouquet.

Some Old World regions require minimum bottle-aging periods for their wines. The most famous example of this is the minimum aging period established for Champagne.

In Italy, Riserva Chianti must be aged for two years and three months in bottle (these wines released on the third January 1st after harvest). Brunello must be aged four years from the January following the harvest, while Riserva must spend five and of this time, two years must be spent in wood barrels. Barolo must be aged for three years, and Riserva for 4 1/2 years, with one year minimum in wood. Barbaresco must be aged 21 months total with a minimum of 9 months in wood, and Riserva must be aged 45 months.

In Spain, the laws of all regions have been changed to ensure the same minimum aging requirements for each. Vino Joven is aged less than Crianza, which must be aged two years total (with at least 12 months in oak) for reds and one year total (half of that in oak) for white and rosé Crianzas. Reservas must be aged three years minimum with at least one year in oak (two years total with 6 months in oak for whites and rosés), and Gran Reservas must be aged two years in oak and three years in bottle for reds, and four years total with 6 months minimum in oak for rosés and whites. All Cavas, produced using the same methods as Champagne, must spend at least 9 months aging on the lees.

Muscadet sur lie, which derives much of its character from the lees aging, must be aged at least through the winter and be bottled directly off the lees from the beginning of March through the end of June (when 80% of the wines are bottled), or from the 15th of October through the end of November. The wine may be sold only starting on the third Thursday in the March following the harvest. The wine with the shortest minimum aging requirement is probably Beaujolais Nouveau which cannot be released before the third Thursday in the November following the harvest.